This proposal presents an immunotherapeutic strategy for the treatment of cocaine addiction in which catalytic antibodies are evolved for their ability to hydrolyze cocaine to its non-psychoactive products, ecognine methyl ester and benzoic acid. Using previously identified cocaine catalysts, termed GNL, as a starting point, two different directed evolution techniques will be applied for the construction of novel scFv libraries. The first involves affinity maturation by complementarity determining region (CDR) walking based on unpublished crystal structure results from the Wilson and Janda laboratories, while the second relies on random recombination, or deoxyribose nucleic acid (DMA) shuffling. These GNLM (GNL-mutant) libraries will be screened using high throughput methodology and assessed for their ability to hydrolyze cocaine; the top two antibodies will be determined by a comparison their kinetic parameters. Selected GNLM catalysts will be examined for their ability to affect locomotor activity in rats, since motor behavior provides a sensitive and reproducible measure of drug action under standardized conditions.